Process for the propane fractionation of lubricating oil stocks



Oct. 24, 1950 A. N. DE VAULT PROCESS FOR THE PROPANE FRACTIONATION 0F LUBRICATING on. sTocKs Filed Nov. 7, 1949 III.

III

IN VEN TOR.

w W E D N A A TTORNEVS Patented Oct. 24,

PROCESS FOR THE PROPANE FRACTIONA- TION OF LUBRICATIN G OIL STOCKS .Albert N. De Vault, Bartlesville, Okla, assignor to-Phillips Petroleum Company, a corporation of Delaware Application November 7, 1949, Serial No. 125,986

7 Claims. 1

This invention relates to the propane fractionation of lubricating oil stocks. In one aspect it relates to a process for the propane fractiona tion of asphalt-containing lubricating oil stocks. In another aspect it relates to a method for the propane fractionation of asphalt-containing lubricating oil stockslwherein the process is one of continuous operation and Without plugging of the fractionating column with solid or semisolid asphaltic material. H I

The asphalt content of a crude oil may be defined asthe per cent-,pf residue from the vacuum distillation of a crudeoil having a maximum A. S; T. M. D234-36fpenetration of 100 at 77 F.

'Some asphalt containing crude oilstocks contain as little as 2 per cent by weight or even less asphalt. Many asphaltic crude oils, such as California crudes, containfrom 12 per cent to 65 per cent asphalt, and Wyoming and Arkansas crude oils contain about 30 per cent asphalt. It

will be obvious that crude oils which contain this relativel high percentage of asphalt will produce reduced crude oil stocks containing much higher percentages of asphalt. The reduction of crudeoils, of course, consists in the removal of dissolved hydrocarbon gases, gasoline, kerosene and distillatefractions, leaving as a residue the lubricating constituents with or Without asphaltic constituents.

The high asphalt content crude oil stocks tinuous process for the fractionation of lubricating oil stocks with liquid propane.

Another object of this invention is to provide a process for the fractionation of asphaltic-containing lubricating oil stockswherein asphaltic material is not deposited in a propane fractionating column.

Still another object of my invention is to provide a combination process for the removal of asphaltic material from asphalt-containing crude lubricating oil stocks and the subsequent separation of lubricating oilfr'actions with liquid propane.

Still other objects and advantages of my process will be obvious to those skilled in the art upon reading the following description which, taken with the attached drawing, forms a part of this specification.

The drawing represents diagrammatically one form of apparatus in which to practice the process of my invention.

The separation of liquid asphaltic materials from petroleum oils and more particularly from reduced crude oils by means of single-stage extraction with propane is old in the art. Such operations are usually carried outat moderate temperatures in the range of about to 160 F.

inv the case of Mid-Continent residua to yield asphaltic fractions of varying amounts depending on asphaltene content, temperature and propane/oil ratio employed. In addition to this conventional de-asphalting type of operation, it has been recognized for many years that a fractionating effect can be realized in the case of propane-oil mixtures subjected to temperatures in the region of F. up to the critical temperature of propane. This fractionation effect is a direct result of the unique properties of propane-oil systems wherein high molecular weight components of the oil and the most aromatic are rejected from solution with increasing temperature. Thus in countercurrent towers using a stripping section and a temperature differential in therectifying section, an effect equivalent to distillation and solvent extraction may be achieved. However, due to difficulties imposed by operating in close proximity to the critical temperature of propane, commercial not hitherto reported in the prior art. The most troublesome problem is that presented by the separation of an asphaltic phase inthe countercurrent tower, which renders the process inopere.

ative in the case of high-asphalt stocks and in many representative low-asphalt mid-continent residual stocks. In the propane fractionation of three wellrknown and representative reduced crud'es from widely separated Oklahoma fields, tw'owere found to be unsuitable to this type of fractionation because of deposition of solid asphaltic plugs in the column. In general, each reduced crude oil feed stock was subjected to the following fractionation conditions to produce SAE oils during the operative periods: propane/oil volume ratio, 7/1; top tower temperature, about 195 F.; bottom tower temperature, about 175 F. In the cases of the two intractable stocks the asphalt deposits built up throughout the entire length of the stripping section until virtually complete closure of the column occurred.

The exact mechanism involved in the formation of asphaltic plugs from these low asphalt stocks is not understood, nor can the usual inspection tests be relied upon to indicate which crudes are amenable to this type of fractionation. The evidence strongly indicates that in the case of certain Mid-Continent residue three phases are formed in the vicinity of the feed plate, (1) a propane-rich light oil fraction, (2) an oil-rich propane-oil solution, and (3) a semi-solid asphalt-oil solution. These facts have been verified by equilibrium bomb experiments carried out at feed plate conditions, which experiments are the only reliable index as to the amenability of a given reduced crude to propane fractionation. The actual quantity of oil-free asphaltenes involved in'inoperative stocks is ver small, being of the order of 0.05 to 1.0 per cent by weight as determined in the equilibrium bomb. The seriousness of the problem is further emphasized by the fact that the oil-free asphaltenes found in a completely plugged column amounted to only 10 per cent of the available free asphalt formed at. the feed plate during the operating period. This apparent paradox is resolved on consideration of the fact that the solid plug contains from to per cent oil, thus greatly increasing the bulk of the asphaltic material. It has further been found that in the case of troublesome stocks, variations in temperature, pressure, and propane/oil ratio do not materially influence the phase relationships previously set forth.

I have now discovered a procedure whereby all crudes regardless of type can be rendered adaptable to propane fractionation. My process involves de-asphaltizing by dilution of the reduced crude with 2 to 10 volumes of propane at temperatures of from 75 F. to F. and separating an asphalt and an oil phase as in conventional de-asphalting of such stocks. The relatively large amount of propane contained in the deasphaltized oil is deleterious to the subsequent fractionating step and must be removed. Conventional removal of excess propane is carried out by distillation which is a costly procedure involving stripping columns, condensers, heaters, compressors and the like. My process entails heating of the de-asphaltized oil-propane solution, as it comes from the asphalt settler, to near or above the critical temperature of propane. Under these conditions a separation of the mixture into two phases occurs, resulting in a'substantially complete separation into oil-free propane as one phase and an oil-rich phase of greatly lowered propane content as the other phase. The large difference in density of the two resulting phases promotes easy and rapid separation. The only work needed on this recovery system is the relatively small quantity of heat required to raise the temperature of the de-asphaltized oil-propane mixture to .the separation temperature. Since in any case the feed to the fractionator must be heated to approximately F. if an overhead SAE 40 to 50 oil is desired, the additional heat required for the separation is merely that required to increase the temperature from about 180 F. to the range of 205 to 225 F. Furthermore, this extra heat can be recovered efiiciently by means of heat exchangers. The propane recovered from the separation process is charged to the fractionating column at the conventional point admixed with fresh makeup propane or at a point between the oil and propane inlets.

Referring now to the drawing, reference numeral 6 identifies a settling tank which is tilted slightly from horizontal. This settler 6 is equipped with several inlet and outlet connections. Pipe 28 is for withdrawal of material from the bottom of the settler. Pipe I is for withdrawal of material from the top of the settler, while inlet 5 is a mixing device of the type of a mixing orifice or a vertical mixer or any other type of mixer which is adapted to mixing of liquid propane and an asphalt-containing lubricating oil stock at the point of introduction of the mixture into the settler tank 6. Reference numeral 8 refers to a heating coil disposed in the heater box 9. This box 9, of course, may be a fire box chamber lined with fire brick or suitable refractory to withstand any temperatures for applying heat to the coil 8. The coil heater assembly 89 may alternately be a heat exchanger in which superheated steam is passed in Vessel 'II is an elongated. vertically disposed vessel used for the. separation of two phases.

. Heat exchanger 3 is provided for exchanging of heat between material leavin the top of vessel II through a line I6 and material introduced into the system through some lines I and 2. Material exiting from the exchanger 3 may pass through line 4 for passage into the mixing device 5. Settler II is provided with a bottoms draw-off line I2 and this line I2 is connected with a heat exchanger I3 similar to exchanger 3. Material from the bottom of vessel I I is intended to enter exchanger'l3 through line I2 and to leave through a line I4 while material passed in heat exchange enters the system through a line 26 and leaves the exchanger through a line 21.

A vessel I5 is a fractionating vessel in which the lubricating oil stock may be fractionated with liquid propane under high pressures. This vessel is equipped with an overhead product withdrawal line 22, a bottoms withdrawal line 2 I, and several side inlet lines. Line I4, previously mentioned, is connected with about the center vertically of the vessel I 5, while inlet lines I8 and I9 are connected with vessel I5 at progressively lower points.

Vessel 23 is a fractionating tower having an overhead vapor product withdrawal line 29, a side inlet line which connects with the overhead line 22 from vessel I5, and a bottom withdrawal line 24. A reboiler coil 25 is provided for the reboiler section of this still. Line 52 is for introduction of reflux from any source desired.

A condenser 30 is connected with the end of line 29 for the condensation of material passing from line 29 into a line 3|.

A line II] is connected with the outlet from the heating coil 8 to an inlet point in about the middle of the settler II. A pipe I! is provided for passage of one of the materials issuing from the heat exchanger 3 to lines I8 and I9. Line 20 is for passage of material from a source, not shown, into lines I9 and I8.

In the operation of my process, an asphaltcontaining reduced crude lubricating oil stock from a source not shown enters the system through the line 28 and is heated in heat exchanger IS. This heated oil then passes on through the line 21 to the mixer 5. Liquid propane, either recycled propane as subsequently produced, or fresh propane, or a mixture of the two, is passed through the line 2 and through the heat exchanger 3 in which the charge propane is heated. The heated propane from the exchanger 3 is conducted through the pipe 4 to the mixer 5. This mixer 5 is intended to mix thoroughly and completely the propane from line t and the asphalt-containing oil stock from line El, and to discharge the mixture into the settler 6. This mixer 5, as mentioned before, may be any type of mixer suitable for mixing such materials. The mixer'may be installed and operated in such a manner asto discharge the mixture into the settler tank 6, or the mixer 5 may be installed within the settler tank 6, if desired. According to m process, I mix one volume of asphalt-containing crude oil stock with from 2-10 volumes of propane at a temperature between about 75 F. and 160 F. The pressure maintained in this tank is, of course, sufficiently high to make certain that the propane is a liquid under the temperature conditions mentioned. This pressure may be from about 580 lbs. to 650 p. s. i. g. Under these operating conditions, an asphaltic oil settles to the bottom of the vessel 6, while the upper propane layer 4| contains the desired lubricating oily constituents, along with undesired oily constituents. The asphaltic constituents, however, are well segregated in the asphaltic layer 52. The liquid asphalt-containing layer 42 is continuously withdrawn through the line 28 to such disposal as desired. This disposal may include a propane separation apparatus in which propane dissolved in the asphaltic material is separated by flashing or by distillation, condensed and recycled into the system. Propanefrom this source for recycling may be introduced into the system from pipe 3 for passage through the mixer 5, or may be introduced into the system through the line for passage through pipes is or I 8 into the fractionation vessel I 5.

The propane-oil phase 4| is removed from the settler 5 through the line I and is conducted to the heating coil -8. Heated material from coil 8 is passed through line I0 into about a mid-point of the settler II. In heating coil 8, the propaneoil solution is heated to a temperature of from 205-225 F. At this relatively high temperature, most of the lubricating oil stock is thrown out of solution in propane and separates as a separate phase. This phase, which is specifically heavier than the propane phase, settles to the bottom of the vessel II and accumulates therein as a liquid phase, identified by reference numeral 44. This liquid phase is accordingly ah oily phase containing only a relatively small amount of dissolved 6. of oil and, of course, material of this composition is the charge to the settler I I The propane-rich phase 43' from separator II is removed from this vessel through the overhead line It to the heat exchanger 3, in which the propane product is cooled. The cooled propane solution containing the small amount of oil is passed on through the pipe I"! and is introduced into the fractionator I 5 through the side inlet pipe I 9.

The oil-rich phase accumulating in the bottom of the separator vessel I l is removed through the pipe I2 and cooled in the exchanger I3. The cooled oil is passed on through pipe I5 and introduced into thefractionator vessel I5 at about a mid-point vertically. The phases are separated in separator II, prior to introduction into fractionator I5 in order to maintain a proper propane to oil ratio at the different points in the iractionator column. An oil-rich phase 45 is maintained in the bottom of this fractionator vessel I5, while a propane-rich phase is maintained as an upper layer as. This upper propane layer 455 contains the paraflinic and more desirable lubricating oil constituents which are stripped from the oil phase 45 by propane introduced through line I9. In the vessel I5 and connected to the end of line I9 is a distributor ring or other means for providing a large surface of contact between the introduced propane and the oil phase 45. Some oily material of course is dissolved from the oil introduced through line- I4 as the oil settles in countercurrent relation to the upward-rising propane. Reference numeral 41 is intended to indicate the liquid-liquid interface between the upper propane-rich layer 45, and the bottom oil-rich layer 46. The section of the vessel below the inlet I 5 may be termed the stripping section, while the section of the vessel above inlet I l may be termed the fractionating zone. The propane containing the small amount of dissolved oil introduced into the vessel I5 through line I9 is introduced at such a temperature that the section of the fractionator below the interface 41 may be maintained at a temperature between the limits of about and 180 F. The charge oil introduced into the fractionator through pipe It is introduced at such a temperature that at its point of addition the contents of the tower are maintained at a temperature between limits of and 190 F. Means for heating the top of the vessel to a still higher temperature is represented by a heating coil 5| positioned in the top of the tower. A heat exchange material is passed through the coil 5I at such a temperature and in such an amount as to maintain a temperature in the top of. the fractionator between the limits of and 200 F. The pressure in. fractionatcr i5 is usuall about 580-650 p. s. i. At higher temperatures the more naphthenic and aromatic, and the higher molecular weight parafnnio constituents are precipitated from solution in propane. Thus by maintaining the propane solution at the upper outlet end of the fractionator at a desired temperature, the propanesolution will contain desired lubricating oil constituents. The propane-oil product leaving vessel I5 through line 22 is conducted int fractionator vessel 23. In the fractionator 23 sufficient reboil heat is supplied throughthe reboiler 25 to separate the propane from the lubricating oil constituents at a lower pressure than that in fractionator I5. The lubricating oil constituents are accordingly removed from the bottom of the fractionator through the line 24 for such subsequent treatment'or disposal as desired. The Va;-

porous propane is removed through the overhead vapor line 29, is condensed in condenser 30, and the condensate passed through line 3| into line 2 as recycled propane. New or fresh propane, needed for make-up purposes or for charging the propane-to-oil ratio in the system, may be at least in part added through line I. Additional propane for make-up purposes and especially as required for direct use in the fractionator I5 is introduced through the line for addition to the propane passing from line I! into the line I9.

If desired, the propane from line I! may be introduced into the fractionator I5 in the fractionating section through the inlet pipe I8 in place of through line I9 into the stripper section. If desired, the propane from line Il may be introduced int the fractionator through lines I8 and I9. Ordinar pressure in the asphalt settler 6 may be somewhat higher than in subsequent'apparatus along the route of travel of the propane solution, but only sulficiently higher as to cause the material to flow without the use of pumps from the settler 6 through the coil 8, settler II, and into and out of the fractionator I5.

An overall propane-to-oil ratio is maintained between the limits of 6:1 to 14:1.

Example In one embodiment of the present invention, a Mid-Continent residuum is treated according to the process hereinabove described. Liquid propane is passed through line 2 and heated in exchanger 3 to a temperature of about 130 F. and passed through line 4 to mixer 5. The crude oil stock residuum is passed from line 26 into exchanger I3 in which it is heated t about 130 F. This heated oil is then passed through pipe 21 to mixer 5 in which the propane and residuum are thoroughl mixed. The mixture is injected into the settler 6. Approximately 10 per cent by volume settles to the bottom as layer 42. This phase, which is quite fluid and non-fouling in nature, contains approximately equal volumes of propane and oil under conditions of temperature mentioned, and under a pressure of 580-650 p. s. i. g. The asphaltic phase is continuously withdrawn for recovery of propane and asphalt. The upper propane-oil phase which contains about one volume of oil dissolved in about 5.5 volumes of propane is continuously removed from the settler, is heated to 210-220 F. in heating coil 8, and is then introduced into the propane separator II in which stratification into an oil-rich bottom layer and a propane-rich upper layer occurs. The oil-rich phase contains from .2 to .6 volume of propane per volume of oil, while the propane phase contains only a very small amount of oil, usually less than 0.50 per cent by volume. The propane layer is withdrawn from separator I I and is cooled in exchanger 3 to 175 F. and is intro-' duced through line I9 into a lower portion of the fractionator I5. The oil phase from the separator I I is cooled in exchanger I3 to 180 F. and is introduced into the fractionator- I5 at about a mid-point. The interface between the oil phase and the propane phase in the fractionator is maintained at about a relative position indicated in the drawing. To produce an overhead oil of 78 to 82 S. U. S. viscosity at 210 F., the fractionator is operated under the following conditions: top lower temperature, 195 F.; feed plate temperature1 80 F.; and bottom temperature, 175 F. An overall propane-tooil ratio of 8:1 is maintained, and the pressure is held constant for the entire system at 640 an overheadvapor condenser.

p. s. i. g. When a pressure of 640 lbs. is maintained in the-fractionator I5, pressures at upstream points are slightly higher to overcome resistance of fluid flow. The overall propane-to-oil ratio mentioned takes into consideration the propane contained in the oil feed entering at the feed plate, as well as makeup propane from line 20, and the propane from the top of the separator I I.

If it is desired to operate the fractionator I5 at a slightly lower pressure, slightly lower temperatures in the column may be used. However, sufficient pressure must be used at all times to maintain the entire contents of the fractionator in the liquid or dense phase.

In conventional processes involving propane deasphalting and propane fractionation, propane is separated from the asphalt-free propane-oil solution by distillation. Such an operation involved the use of a fractionator, pumps, reboil heat, and The use of such apparatus in a high pressure system is, of course, expensive to construct and operation costs are high. In my process, I heat the alphalt-free propane-oil solution from the propane separation temperature to a temperature between approximately 205 and 225 F., at which temperature the oil is nearl insoluble in propane. Thus, physical separation between the oil and propane is easily accomplished since there is a considerable spread in specific gravity of these two materials. While some cost is involved in heating the oilpropane mixture to this temperature, the actual cost of this operation is minimized since the propane solution and charge oil to the fractionator have to be heated to to F. for efiicient fractionation and the production of a desired grade of oil. Thus, the net cost of effecting the phase separation between the oil and propane in the separators II is of heating from 175- 180 F. to 205.-225 F. In actual practice, even this amount of heating is not a direct cost item since propane feed to the mixer 5 is heat exchanged with the propane phase from the separator II, and the oil phase from the separator is likewise heat exchanged with the incoming crude residuum. Thus, my system may be operated for considerably less cost than a conventional system, as mentioned above, involving separation of the propane from the oil by distillation methods prior to the oil fractionation step.

M process is not limited to any particular type of reduced crude lubricating oil charge stock. De-asphalting conditions will, of course, vary with the type of charge oil involved. The temperature to be maintained in the phase separator II will, of course, be dependent upon the extent of separation of the oil from the propane desired, and likewise, the temperatures and temperature differentials to be maintained in the fractionator I5 will be dependent upon the grade of oil desired to be taken overhead. The recovery of the propane from the de-asphalted oil and its reuse in the subsequent propane fractionation step will be operative regardness of the relative volumes of propane and oil required in the asphalt removal step within the stated limits.

The oil phase containing some propane in solution issuing from the fractionator I5 through the line 2| may be conducted to a second oil fractionation step similar to that carried out in fractionator I5, but for the production of a hi her viscosity grade of il. If desired, of course, the oil phase from pipe 2I may be passed to a fiash separator or a still for separation of the propane and oil. The propane thus separated may be combined with the propane from the fractionator 23 for recycling into the asphalt settler 6. Like- Wise, a portion of this recycle propane may be introduced through line 20 along with makeup propane as needed. Additional propane to the system may be introduced through line 20 directly to the fractionator IE or through line I directly to the asphalt settler 6, or into both the fractionator l and the settler 6.

Materials of construction may be selected from among those commercially available. Special corrosion resistant materials need not ordinarily be used since in the treatment of such oils corrosion problems are small. However, the apparatus of such a system will need to be constructed to withstand safely pressures of operation as hereinabove described. Such auxiliary apparatus as pumps, valves, temperature and pressure indicating and recording devices, are not shown in the drawing, nor described in the specification, for purposes of simplicity. Likewise, pressure and temperature controllers or flow controller apparatus are not shown. The installation and use of such auxiliary apparatus is well understood by those skilled in the art.

The above-described flow system and operating conditions are given for illustrative purposes and should not be regarded as limiting the invention, the scope of which is set forth in the following claims.

Having described my invention, I claim:

1. A process for the fractionation of asphaltcontaining lubricating oil stocks comprising maintaining a body of propane rich in dissolved oil in a first treating zone and a body of asphaltic material containing dissolved propane below said body of propane rich in dissolved oil in said zone, said bodies meeting at a common interface, introducing propane and said asphalt-containing lubricating oil stock into said zone, removing said asphaltic material containing dissolved propane from said zone; maintaining a body of propane lean in dissolved oil in a second zone at a temperature above that maintained in said first zone and a body of an oil-rich phase containing propane below said body of propane lean in dissolved oil in said second zone at said temperature, said bodies in said second zone meeting at a common interface, removing propane rich in dissolved oil from said first zone, and heating this latter removed material and introducing same into said second zone; maintaining a body of propane containing dissolved oil in a third zone and a body of an oilrich phase below said body of propane containin dissolved oil in said third zone at a temperature below said temperature maintained in said second zone, said bodies in said third zone meeting at a common interface, removing propane lean in dissolved oil from said second zone, cooling this latter removed material and introducing this removed and cooled material into said third zone at a point near said interface, removing oil-rich phase from said second zone and cooling this latter removed material and introducing this cooled material into the body of propane containing dissolved oil in said third zone at a point above the point of introduction of said propane lean in dissolved oil, removing oil-rich phase and propane containing dissolved oil from said third zone, and recovering oil from this latter removed oil-rich phase and oil from this latter propane containing dissolved oil as products of the process.

2. A process for the fractionation of asphaltcontaining lubricatin 011 stocks comprising maintaining a body of propane rich in dissolved oil in a first treating zone and a body of asphaltic material containing dissolved propane below said body of propane rich in dissolved oil in said zone, said bodies meeting at a common interface, introducing propane and said asphalt-containing lubricating oil stock into said zone, removing said asphaltic material containing dissolved propane from said zone; maintaining a body of propane lean in dissolved oil in a second zone and a body of an oil-rich phase containing propane below said body of propane lean in dissolved oil in said second zone, said bodies in said second zone meeting at a common interface, removing propane rich in dissolved oil from said first zone, and in-' troducing same into said second zone; maintaining a body of propane containing dissolved oil in a third zone and a body of an oil-rich phase below said body of propane containing dissolved oil in said third zone, said bodies in said third zone meeting at a common interface, removing propane lean in dissolved oil from said second zone, and introducing this removed material into said third zone at a point near said interface, removing oil-rich phase from said second zone and introducing this material into the body of propane containing dissolved oil in said third zone at a point above the point of introduction of said propane lean in dissolved oil, removing oil-rich phase and propane cotaining dissolved oil from said third zone, and recovering oil from this latter removed oil-rich phase and oil from this latter propane containing dissolved oil as prodnets of the process.

3. In the process of claim 1 maintaining the temperature of the liquid phases in the first zone between the limits of and F., the temperature of the phases in the second zone between the limits of 205 and 225 F., and the temperatures in the top, bottom, and at the oil-rich phase feed point of said third zone between the respective limits of and 200 F., 140 and 180 F., and 160 and F., and maintaining the pressure in the system within the limits of 580 and 650 pounds per square inch.

4. In the method of claim 3, maintaining the volume ratio of the propane to charge oil feed to the first zone between the limits of 2 to 10, and maintaining the overall volume ratio of propane to oil introduced into the third zone between the limits of 6:1 and 14:1.

5. In the method of claim 1 maintaining the temperature of the phases in the first zone at 130 F., the temperature of the phases in the second zone at 205 F., and the temperatures in the top, bottom, and oil phase feed point in the third zone at the respective temperatures of F., 175 F., and 180 R, and maintaining the pressure in the system at 640 pounds per square inch gauge.

6. In the method of claim 5, maintaining the volume ratio of the propane to charge oil feed to the first zone at 5 to l, and maintaining the overall volume ratio of propane to oil introduced into the third zone at 8 to 1.

7. In the process of claim 1 recovering the propane from the latter removed oil-rich phase, from the oil from the said last propane containing dissolved oil and from the removed asphaltic material containing dissolved propane and recycling said recovered propane to the system.

ALBERT N. DE VAULT.

No references cited.

Certificate of Correction Patent No. 2,527,404 October 24, 1950 ALBERT N. DE VAULT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 14, for B23436 read B24336; column 7, line 71, for the word lower read tower; column 8, line 65, for regardness read regardless; column 10, line 30, for cotaining read contaz'mng;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 20th day of February, A. D. 1951.

THOMAS F. lHUR-PIIY,

Assistant OOmmz'ssz'oner of Patents. 

1. A PROCESS FOR THE FRACTIONATION OF ASPHALTCONTAINING LUBRICATING OIL STOCKS COMPRISING MAINTAINING A BODY OF PROPANE RICH IN DISSOLVED OIL IN A FIRST TREATING ZONE AND A BODY OF ASPHALTIC MATERIAL CONTAINING DISSOLVED PROPANE BELOW SAID BODY OF PROPANE RICH IN DISSOLVED OIL IN SAID ZONE, SAID BODIES MEETING AT A COMMON INTERFACE, INTRODUCING PROPANE AND SAID ASPHALT-CONTAINING LUBRICATING OIL STOCK INTO SAID ZONE, REMOVING SAID ASPHALTIC MATERIAL CONTAINING DISSOLVED PROPANE FROM SAID ZONE; MAINTAINING A BODY OF PROPANE LEAN IN DISSOLVED OIL IN A SECOND ZONE AT A TEMPERATURE ABOVE THAT MAINTAINED IN SAID FIRST ZONE AND A BODY OF AN OIL-RICH PHASE CONTAINING PROPANE BELOW SAID BODY OF PROPANE LEAN IN DISSOLVED OIL IN SAID SECOND ZONE AT SAID TEMPERATURE, SAID BODIES IN SAID SECOND ZONE MEETING AT A COMMON INTERFACE, REMOVING PROPANE RICH IN DISSOLVED OIL FROM SAID FIRST ZONE, AND HEATING THIS LATTER REMOVED MATERIAL AND INTRODUCING SAME INTO SAID SECOND ZONE; MAINTAINING A BODY OF PROPANE CONTAINING DISSOLVED OIL IN A THIRD ZONE AND A BODY OF AN OILRICH PHASE BELOW SAID BODY OF PROPANE CONTAINING DISSOLVED OIL IN SAID THIRD ZONE AT A TEMPERATURE BELOW SAID TEMPERATURE MAINTAINED IN SAID SECOND ZONE, SAID BODIES IN SAID THIRD ZONE MEETING AT A COMMON INTERFACE, REMOVING PROPANE LEAN IN DISSOLVED OIL FROM SAID SECOND ZONE, COOLING THIS LATTER REMOVED MATERIAL AND INTRODUCING THIS REMOVED AND COOLED MATERIAL INTO SAID THIRD ZONE AT A POINT NEAR SAID INTERFACE, REMOVING OIL-RICH PHASE FROM SAID SECOND ZONE AND COOLING THIS LATTER REMOVED MATERIAL AND INTRODUCING THIS COOLED MATERIAL INTO THE BODY OF PROPANE CONTAINING DISSOLVED OIL IN SAID THIRD ZONE AT A POINT ABOVE THE POINT OF INTRODUCTION OF SAID PROPANE LEAN IN DISSOLVED OIL, REMOVING OIL-RICH PHASE AND PROPANE CONTAINING DISSOLVED OIL FROM SAID THIRD ZONE, AND RECOVERING OIL FROM THIS LATTER REMOVED OIL-RICH PHASE AND OIL FROM THIS LATTER PROPANE CONTAINING DISSOLVED OIL AS PRODUCTS OF THE PROCESS. 